Switching device for electromagnetic motor starters

ABSTRACT

A switching device for motor starters comprising a basic block and as required one or more adder blocks, the basic block being mountable on the side of a contactor and having two electrically separate circuits, one NO and one NC, the basic block including two pairs of stationary contact tips and two pairs of movable contact tips cooperable therewith, the latter being mounted for movement relative to a plunger which itself is supported for movement relative to the housing of the basic block, the adder block being mountable to an end wall of the basic block, the adder block including both NO and NC stationary contact tips and a movable plunger which supports a convertible contact tip for movement relative thereto, the position of the convertible contact tip relative to the movable plunger being arrangeable such that the former may be made to cooperate with either the NO or NC stationary contact tips of the adder block to provide the latter with either a NO or NC mode of operation, and the movable plunger of the adder block including means formed integrally therewith engageable with corresponding means suitably provided on the movable plunger of the basic block when the adder block is mounted to the basic block.

United States Patent Hughes Feb. 8, 1972 [54] SWITCHING DEVICE FOR ELECTROMAGNETIC MOTOR STARTERS [72] Inventor: Philip G. Hughes, Bloomington, Ill.

[73] Assignee: General Electric Company [22] Filed: Apr. 16, 1970 [21] Appl. No.: 29,062

.....200/16 A Mullen et a1 ..200/166 Bl-l Primary ExaminerR. F. Staubly Assistant Examiner-J. G. Smith Attomey-Arthur E. Foumier, Jr., David M. Schiller, Joseph B. Forman, Frank L. Neuhauser and Oscar B. Waddell [57] ABSTRACT A switching device for motor starters comprising a basic block and as required one or more adder blocks, the basic block being mountable on the side of a contactor and having two electrically separate circuits, one NO and one NC, the basic block including two pairs of stationary contact tips and two pairs of movable contact tips cooperable therewith, the latter being mounted for movement relative to a plunger which itself is supported for movement relative to the housing of the basic block, the adder block being mountable to an end wall of the basic block, the adder block including both NO and NC stationary contact tips and a movable plunger which supports a convertible contact tip for movement relative thereto, the position of the convertible contact tip relative to the movable plunger being arrangeable such that the former may be made to cooperate with either the NO or NC stationary contact tips of the adder block to provide the latter with either a NO or NC mode of operation, and the movable plunger of the adder block including means formed integrally therewith engageable with corresponding means suitably provided on the movable plunger of the basic block when the adder block is mounted to the basic block.

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PHILIP HUGHES ATTORNEY SWITCHING DEVICE FOR ELECTROMAGNETIC MOTOR STARTERS BACKGROUND OF THE INVENTION 1. Field of the Invention My invention relates to electromagnetic starters, and more particularly to an improvement in switching devices of the type which are intended for use with such motor starters and which are constructed so as to provide either normally open (NO) or normally closed (NC) contact operation.

2. Description of the Prior Art In accordance with the teachings of the prior art, it is well known to provide electromagnetic control devices such as magnetic motor starters with switching devices for use as auxiliary contacts or interlocks. Thus for example, such switching devices in the past have been utilized to increase the versatility of magnetic starters by providing the latter with additional control circuits capable of performing a variety of functions. Some exemplary uses to which these additional control cir cuits have been put include among other things the control sequencing of other motor starters and the energization of accessory equipment such as indicating lights.

To facilitate the mounting of this type of switching device to motor starters as well as for purposes of achieving the desired performance therefrom in a given application, it has been found that such switching devices should embody certain features. In this regard, the switching device should include a housing of relatively small size such that when accommodated on the smaller sizes of motor starters, the switching device housing will not exceed the external dimensions of the motor starters. On the other hand for purposes of standardization of parts in the interest of obtaining economies of manufacture, it is desirable that the same size switching device be useable with all of the various sizes of motor starters. This means that the switch device housing which is capable of being mounted to the smallest size of motor starters must also be capable of housing therewith components which are mechanically and electrically compatible with the corresponding components of the larger size of motor starters with which the former components are intended to coact.

Also it is desirable that the switching device by provided with mounting means which will enable the switching device to be mounted to a given motor starter without the need to utilize any special tools or equipment. That is, the switching device should be capable of being easily installed and removed from a motor starter at the point of use rather than be limited to assembly at the point of manufacture. Based on past experience, the switching device should also be constructed so as to provide either NO or NC contact operation at the option of the user. Preferably the user should be able to exercise his choice at the point of the use rather than at the time of purchase. Finally the switching device should be compatible with other similarly constructed switching devices such that a plurality of switching devices mechanically interconnected in series may be mounted to a motor starter without substantially increasing the overall physical dimensions of the motor starter while yet enabling the motor starter to be provided with a plurality of additional control circuits.

Although a number of attempts have been made to devise a switching device which would be capable of use as an auxiliary contact or interlock and which would incorporate all of the features referred to hereinabove, the prior art switching devices have proven to be deficient in one or more aspects such as for example their relative size, or the difficulty of mounting them to a motor starter, or their incompatibility with other similarly constructed switching devices or the number of additional contact circuits which they permit to be added to a given motor starter. An example 'of a prior art interlock switching device is found in US. Pat. No. 2,918,554.

OBJECTS OF THE INVENTION It is therefore an object of the present invention to provide a novel and improved switching device for electromagnetic control devices such as magnetic motor starters which is embodied in a housing which remains of the same size regardless of the size of the motor starter with which the switching device is employed. 1

It is another object of the present invention to provide such a switching device which is capable of being mounted to a motor starter at the point of use rather than at the point of manufacture and which for purposes of mounting does not necessitate the use of any special tools or equipment.

A still further object of the present invention is to provide such a switching device which is constructed so as to provide either NO or NC contact operation at the option of the user at the point of use rather than at the time of purchase.

Yet another object of the present invention is to provide such a switching device which may be mechanically interconnected in series with other similarly constructed switching devices and then mounted to a motor starter whereby the number of additional control circuits with which the motor starter is provided may be augmented.

Yet a further object of the present invention is to provide such a switching device which achieves all of the foregoing objects, is relatively inexpensive to manufacture, and which most importantly provides in addition reliability and ease of operation.

SUMMARY OF THE INVENTION In accordance with a preferred form of the present invention there is provided a switching device for electromagnetic control devices such as magnetic motor starters which consists of a basic block mountable on a sidewall of a motor starter and having two electrically separate circuits, one NO and one NC, and as required one or more adder blocks mountable on an end wall of the basic block, each adder block having only one circuit. The basic block includes two pairs of stationary contact tips and two pairs of movable contact tips cooperable therewith. The latter are mounted for movement relative to a plunger which itself is supported for movement relative to the housing of the basic block. This movable plunger includes a first lug extending outwardly therefrom which is movable within a slot suitably provided therefor in a sidewall of the basic block housing. A second lug formed as an integral part of the movable plunger protrudes through an opening provided therefor in an end wall of the basic block housing. The latter second lug is capable of engaging a similar lug provided in an adder block.

Each of the adder blocks includes both NO and NC stationary contact tips, and a movable plunger which supports a convertible contact tip for movement relative thereto. The position of the convertible contact tip relative to the movable plunger may be arranged such that the former may be made to cooperate with either the NO or NC stationary contact tip of the adder block to provide the latter with either a NO or a NC mode of operation. A pair of lugs formed integrally with the movable plunger extend outwardly at either end of the adder block through suitable openings provided therefor in each of the end walls thereof. Oneof these lugs is engageable with the previously described second lug of the basic block when the adder block is mounted to the basic block. The second lug of the movable plunger of the adder block is intended to cooperate with a similarly constructed lug of a second adder block for those installations requiring the use of more than one adder block.

The invention will be more fully understood from the following detailed description and its scope will be pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a side elevational view of the basic block of a switching device in accordance with the present invention;

FIG. 2 is an end view of the basic block of the switching device of FIG. 1 in accordance with the present invention;

FIG. 3 is a side elevational view of the basic block of the switching device of FIG. IV with one part of the housing removed to illustrate the internal construction of the basic block in accordance with the present invention, the basic block being shown in a position rotated 90 counterclockwise from its position in FIG. 1 and also rotated 180 about its axis;

FIG. 4 is a side elevational view of the movable plunger of the basic block of the switch device of FIG. 3 illustrated removed from the basic block;

FIG. 5 is a side elevational view similar to FIG. 4 of the movable plunger of the basic block of the switching device of FIG. 3 in accordance with the present invention;

FIG. 6 is a side elevational view of the adder block of a switching device in accordance with the present invention illustrated with one part of the housing removed and with the movable plunger arranged to provide normally closed contact operation;

FIG. 7 is a side elevational view similar to FIG. 6 of the adder block of a switching device in accordance with the present invention but with the movable plunger arranged to provide normally open contact operation;

FIG. 8 is a side elevational view of the movable plunger of the adder block of the switching device of FIG. 6 illustrated removed from the adder block, the plunger being rotated 180 about its axis from its position in FIG. 6;

FIG. 9 is a side elevational view similar to FIG. 8 of the movable plunger of the adder block of the switching device of FIG. 6 in accordance with the present invention; and

FIG. 10 is a side elevational view of the basic block and the adder block of a switching device in accordance with the present invention illustrated in the disassembled condition.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring to FIG. 10 of the drawings, there is illustrated therein a preferred embodiment of the present invention which comprises a switching device, generally designated by reference number 10, intended for use primarily with electromagnetic control devices such as magnetic motor starters. For purposes of illustration and description, the switching device 10 as shown in FIG. 10 includes a basic block 11 and an adder block 12. However, it is to be understood as will become more fully apparent hereinafter that for purposes of some applications the switching device 10 may comprise solely the basic block 11 whereas when used in other applications the basic block 11 may be employed in combination with one or more adder blocks 12. That is, the basic block 11 is constructed so as to be capable of functioning either alone or in combination with a single or a plurality of adder blocks 12.

Turning now to FIGS. 1, 2 and 3 of the drawings and a description of the basic block 11 illustrated therein, the latter block 11 includes a housing 13 which as best seen in FIG. 2 is assembled to a suitable support 14 and a suitable insulation piece 15 in a manner to be more fully set forth hereinafter. The housing 13 which is formed of suitable insulating material of the type well known for use for this purpose to those skilled in the art is provided as seen in FIG. 3 with a substantially hollow compartmentalized interior 16 and an open sidewall 17. In the assembled condition sidewall 17 is closed by an insulation member or cover 18 portions of which are visible in FIGS. 1 and 2 of the drawing. In order to effectively accomplish its insulating function, the insulation member or cover 18 is intentionally made slightly larger than the surface area of open sidewall 17 of basic block 11 which it is intended to cover.

The basic block 11 is provided with a pair of electrically separate circuits, one normally opened (NO) and one normally closed (NC). To this end, the basic block 11 includes two pairs of stationary contact assemblies 19 and 20, respectively, cooperable therewith. As will be described more fully hereinafter, moveable contact assemblies 21 and 22 are mounted for movement relative to a plunger 23 which itself is supported for movement relative to housing 13 of basic block I l.

Referring to FIG. 3 of the drawings, each of the pair of stationary contact assemblies 19 comprises a contact support 24 formed of suitable electrically conductive material. A stationary contact tip 25 is supported at one end of the contact support 24 and the latter is provided at the other end thereof with a conventional terminal 26 consisting of a substantially U-shaped clamp 27 and a clamping screw 28. Each of the stationary contact assemblies 19 is received within a suitable slot 29 provided therefor in the sidewall portions 13a of housing 13 of basic block 11 such that the stationary contact tip 25 is positioned within a compartmentlike segment of the interior 16 of housing 13 and such that terminal 26 is located externally of housing 13 for easy accessibility thereto. Preferably a triangular-shaped projection 30 which engages contact support 24 is provided in each slot 29 as a form of retaining means. That is, with the stationary contact assembly 19 positioned in slot 29, the contact support 24 is essentially held fixed by projection 30 against insulation barrier 31 of housing 13. As illustrated in FIG. 3 of the drawings, the projections 30 as well as the insulation barriers 31 are formed as integral parts of housing 13. However, it is contemplated within the spirit of the invention that both of these elements, i.e., projections 30 and barriers 31 could if desired be in the form of separate members.

Insofar as stationary contact assemblies 20 are concerned, they each include a Z-shaped like contact support 32 formed of suitable electrically conductive material. A stationary contact tip 33 is supported at one end of each of the Z-shaped contact supports 32 and the latter are each provided at the other end thereof with aconveritional terminal 34-consisting of a substantially U-shaped clamp. 35 and a clamping screw 36. The stationary contact assemblies 20 are each supported in a suitable slot 37 provided for this purpose in sidewall portions 13a of housing 13. When so received in slots 37, the stationary contact tips 33 of stationary contact assemblies 20 are each positioned in an individualized compartmentlike segment of interior 16 of housing 13, and the terminals 34 are each located externally of housing 13 in juxtaposed relation to the latters sidewall portions 13a affording easy accessibility thereto. In a manner similar to that described hereinabove in connection with the description of stationary contact assemblies 19, the stationary contact assemblies 20 are retained properly oriented in slots 37 by virtue of the engagement of triangular-shaped projections 38 and hooklike portions 39 of insulating barriers 40 with the Z-shaped contact support 32 of each of the stationary contact assemblies 20. Thus, as illustrated in FIG. 3 the projections 38 and hooklike members 39 function to hold the stationary contact assemblies 20 captive in slots 37.

As best illustrated in FIGS. 3, 4, and 5 of the drawings, the pair of movable contact assemblies 21 and 22, respectively, of basic block 11 are supported on plunger 23 for movement relative thereto while the plunger 23 itself is supported for movement relative to housing 13 of basic block 11. The plunger 23 as seen in FIG. 3 is supported approximately centrally within the hollow interior 16 of basic block 11 and in close proximity to the individualized compartmentlike segments of interior 16 in which the stationary contact tips 25 and 33 of stationary contact assemblies 19 and 20, respectively are located. The plunger 23 comprises an elongated member having a housing 41 formed preferably of the same type of material as that employed in forming housing 13 of basic block 11. At one end, the plunger housing 41 is provided with a hooklike portion or lug 42 for a purpose which will be described subsequently hereinafter. As illustrated, the hooklike portion or lug 42 constitutes an integral part of plunger housing 41 although it might also take the form of a separate member. The other end of plunger housing 41 is provided with a projection 43 slightly smaller in size than the external dimensions of plunger housing 41. The latter projection 43 serves as a seat for one end of spring 44. The other end of spring 44 abuts against wall portion 45 suitably provided for this purpose within the interior 16 of housing 13 of basic block 11. The spring 44 is intended to bias the plunger 23 in an upwardly, i.e., outwardly direction as viewed with reference to FIG. 3 of the drawing.

Housing 41 of plunger 23 is provided with an essentially hollow interior, access to which may be had through two pairs of elongated slots 46 and 47, respectively, located in opposing sidewalls 48 and 49 of housing 41. As illustrated in FIG. 5 of the drawings, only one of each of the pairs of slots 46 and 47 is visible. Movable contact assembly 21, which comprises a contact support 50 formed of suitable electrically conductive material, and a pair of movable contact tips 51 supported at the ends of contact support 50, extends through the interior of plunger housing 41 and projects outwardly therefrom through slots 46 on either side of housing 41 so as to be substantially at right angles to the plane of the correspondingly adjacent opposing sidewall 48 and 49, respectively. As viewed with reference to FIG. 4 of the drawings, the movable contact tips 51 both face inwardly, i.e., downwardly. Also, it is seen with reference to FIG. 5 of the drawing that the movable contact assembly 21 is located at the lower end of slots 46. Spring 52 which is housed within a hollow cavity suitably provided for this purpose in the interior of plunger housing 41 has one end abutting the plunger housing 41 and the other end in engagement with contact support 50 of movable contact assembly 21 whereby the spring 52 biases the movable contact assembly 21 to the aforesaid lower end of slots 46 as viewed with reference to FIG. 5.

Movable contact assembly 22 is of the same construction as movable contact assembly 21. That is, movable contact assembly 22 similarly consists of a contact support identified in this instance by reference numeral 53 and having a pair of movable contact tips 54 supported at the ends thereof. Movable contact assembly 22 extends through the interior of housing 41 of plunger 23 and projects outwardly therefrom through slots 47 on either side of housing 41 so as to be substantially at right angles to the plane of the correspondingly adjacent opposing sidewalls 48 and 49, respectively. As viewed with reference to FIG. 4 of the drawings, the movable contact tips 54 both face upwardly, i.e., towards the movable contact tips 51 of movable contact assembly 21. Also, it is seen with reference to FIG. 5 of the drawings that the movable contact assembly 22 is located at the upper end of slots 47. Spring 55 which is housed within a hollow cavity suitably provided for this purpose in the interior of the plunger housing 41 has one end in engagement with flat elongated member 56 and the other end in engagement with contact support 53 of movable contact assembly 22 whereby the spring 55 biases the movable contact assembly 22 to the aforesaid upper end of slots 47 as viewed with reference to FIG. 5.

Flat elongated member 56 extends through the interior of housing 41 of plunger 23 and projects outwardly therefrom through slots 47. Spring 55 biases the member 56 downward into engagement with the lower end wall surface of slots 47 as can best be seen with reference to FIG. 5 of the drawings. With the plunger 23 positioned in the interior of housing 13 of basic block 11 as illustrated in FIG. 3 of the drawings, the member 56 spans and rests on the mouth of opening 57 in which spring 44 is located and into which opening the lower portion of plunger 23 moves when the plunger 23 is depressed as a result of an external force being applied thereto in a manner to be more fully described hereinafter.

Referring again to FIG. 5 of the drawings, the plunger 23 is provided with an L-shaped lug 58 which extends outwardly from sidewall 59 of the plunger housing 41. Lug 58 is preferably formed as an integral part of the plunger housing 41 whereby the lug 58 is incapable of relative movement relative to housing 41. The tip 60 of lug 58 is of sufficient length so as to project through and beyond the cover 18 as well as the support 14 and insulation piece 15 illustrated in FIG. 2. A suitable opening (not shown) is provided in each of the aforesaid members to permit the tip 60 of lug 58 to project thcrcthrough as well as to permit movement of the lug 58 relative thereto.

Insofar as assembling the various component parts of the basic block 11 is concerned, the stationary contact assemblies 19 and are first positioned in the respective slots 29 and 37, respectively, as illustrate in Flg. 3 of the drawing. Thereafter. with the spring 44 in place in opening 57, the plunger 23 may be slid into place in the interior 16 of housing 13 with the lug 58 extending toward the open wall 17 of basic block housing 13. When so assembled, spring 44 biases plunger 23 upwardly as viewed with reference to FIG. 3 of the drawings such that the contact tips 51 of movable contact assembly 21 are spaced from the contact tips of stationary contact assembly 19 and such that the contact tips 54 of movable contact assembly 22 are in engagement with contact tips 33 of stationary contact assembly 20 so as to make good electrical contact therewith. It is thus seen that stationary contact assembly 19 with which I movable contact assembly 21 cooperates provides the basic block 11 with a normally open (NO) circuit which is electrically separate from the normally closed (NC) circuit created by virtue of the engagement of the contacts of movable contact assembly 22 with those of stationary contact assembly 20. Then, cover 18 is placed in juxtaposed relation to the open sidewall 17 of basic block 11 such that lug 58 projects outwardly through the opening provided therefor in cover 18. With the cover 18 held in place, support 14 is positioned against the outer surface of cover 18. Cover 18 and support 14 are secured in position by suitable fastening means such as a plurality of eyelets 61. As seen in FIG. 1 of the drawings, sidewall 13b of housing 13 of basic block 11 is provided with four spaced openings 62 which extend entirely through the housing 13. Similar openings (not shown) are provided in cover 18 such that when the cover 18 is properly positioned relative to open sidewall 17 of basic block 11, the latter openings (not shown) will be in alignment with the openings 62 and in position to receive the eyelets 61 which pass through the openings in cover 18 and project a suitable distance into the openings 62.

In accordance with the preferred embodiment of the invention, the insulation piece 15 is merely snapped into place in juxtaposed relation to the outer surface of support 14. The support 14 is provided with a pair of suitably dimensioned tabs 63 which are formed by reversibly bending outwardly portions of the support 14. The tabs 63 function to hold the insulation piece 15 in place once the piece 15 has been snapped over the tabs 63. The latter are also employed for the purpose of mounting the basic block 11 to an electromagnetic control device such as a magnetic motor starter, a fragmentary portion of which is shown in dotted lines in FIG. 2. To this end, the magnetic motor starter casing is provided with a pair of suitably spaced slots or grooves dimensioned such as to be capable of receiving the aforesaid pair of tabs 63.

With the basic block 11 mounted to the sidewall casing of the magnetic motor starter by means of tabs 63 in the manner briefly described in the preceding paragraph, lug 58 of plunger 23 is positioned in the path of movement of a suitable projection on the movable member of the magnetic motor starter in a manner similar to that illustrated for example in Us. Pat. No. 2,874,252, the latter patent also being assigned to the same assignee as the present invention. As the aforesaid movable member of the magnetic motor starter moves to its actuated position, it engages the tip 60 of lug 58 thereby causing the lug 58 to also move. Since lug 58 is rigidly affixed to plunger 23, movement of lug 58 is transmitted to the housing 41 of plunger 23 whereby the latter is also caused to move. As viewed in FIG. 2, the lug 58 is moved along an axis perpendicular to the plane of the paper.

Referring to FIG. 3 of the drawings, the position of plunger 23 relative to the interior 16 of basic block housing 13 corresponds to the unactuated position of plunger 23. In moving to its actuated position, the plunger 23 is urged in a downwardly direction against the bias of spring 44. As plunger 23 moves in the aforementioned downward direction, the contact tips 51 of movable contact assembly 21 arebrought into good electrical contacting relation with the contact tips 25 of stationary contact assemblies 19 while the contact tips 54 of movable contact assembly 22 are disengaged from the contact tips 33 of stationary contact assemblies 20. Plunger 23 is returned to the unactuated position under the influence of spring 44. Thus it is seen that regardless of whether or not the plunger 23 is in its unactuated or its actuated position, the basic block 11 always has one electrical circuit which is in open condition and one electrical circuit which is in closed condition. Further it can be seen that the respective condition of the two electrically separate circuits provided in basic block 11 is dependent, when the basic block 11 is mounted to a magnetic motor starter, on the operating condition of the latter.

Turning now to FIGS. 6 and 7 of the drawings and a description of the adder block 12 illustrated therein, in accord with the present invention the adder block 12 includes a housing 63 which is formed of the same type of material as housing 13 of basic block 11. The housing 63 is provided with a substantially hollow compartmentalized interior 64 and an open sidewall 65. In the assembled condition sidewall 65 is closed by an insulation member or cover (not shown) similar to the previously described cover 18 of basic block 11. In order to effectively accomplish its insulating function, the insulating member or cover for adder block 12 is intentionally made slightly larger than the surface area of open sidewall 65 which it is intended to cover.

The adder block 12 is provided with an electrical circuit which is convertible between a normally open (NO) circuit and a normally closed (NC) circuit. To this end, the adder block 12 includes both normally open and normally closed stationary contact assemblies 66 and 67, respectively, and a convertible contact assembly 68 cooperable with either the stationary contact assembly 66 or the stationary contact assembly 67. As will be described more fully hereinafter, convertible contact assembly 68 is mounted for movement relative to a plunger 69 which itself is supported for movement relative to housing 63 of adder block 12.

Referring to FIGS. 6 and 7 of the drawings, each of the pair of normally open stationary contact assemblies 66 comprises a contact support 70 formed of suitable electrically conductive material. A stationary contact tip 71 is supported at one end of the contact support 70 and the latter is provided at the other end thereof with a conventional terminal 72 consisting of a substantially U'shaped clamp 73 and a clamping screw 74. Each of the normally open stationary contact assemblies 66 is received within a suitable slot 75 provided therefor in the sidewall portions 63a of housing 63 of adder block 12 such that the stationary contact tip 71 is positioned within a compartmentlike segment of the interior 64 of housing 63 and such that terminal 72 is located externally of housing 63 for easy accessibility thereto. Preferably the spacing between the sidewalls of each slot 75 is such as to essentially restrict any movement of the normally open stationary contact assembly 66 in the slot once the assembly has been positioned therein.

Insofar as normally closed stationary contact assemblies 67 are concerned, they each include a U-shaped contact support 76 formed of suitable electrically conductive material. A stationary contact tip 77 is supported on one leg portion of each of the contact supports 76 and the other leg portion 78 of each of the contact supports 76 is supported in good electrically conducting relation with the contact support 70 of normally open stationary contact assemblies 66. The normally closed stationary contact assemblies 67 are each supported in a suitable groove (not shown) provided for this purpose in sidewall portion 63b of housing 63. The normally closed stationary contact assemblies 67 are received within the aforesaid groove with a sufficiently tight fit as to preclude any significant relative movement of the assemblies 67 therewithin.

As best illustrated in FIGS. 8 and 9 of the drawings, the convertible contact assembly 68 of adder block 12 is supported on plunger 69 for movement relative thereto while the plunger 69 itself is supported for movement relative to housing 63 of the adder block 12. The plunger 69 as seen in FIGS. 6 and 7 is supported approximately centrally within the hollow interior 64 of adder block 12 and in close proximity to the compartmentlike segments of interior 64 in which the normally open and normally closed stationary contact assemblies 66 and 67, respectively, are located. The plunger 69 comprises an elongated member having a housing 79 formed preferably of the same type of material as that employed in forming housing 41 of plunger 23 of basic block 11. At either end, the plunger housing 79 is provided with a hooklike portion or lug 80 which is capable of mating with the hooklike portion or lug 42 of plunger 23 of basic block 11 or with the hooklike portion of the plunger of another adder block (not shown).

Housing 79 of plunger 69 is provided with an essentially hollow interior, access to which may be had through a pair of elongated slots 81 located in opposing sidewalls 82 and 83 of housing 79. As illustrated in FIG. 9 of the drawings, only one of the slots 81 is visible. Convertible contact assembly 68, which comprises a contact support 84 formed of suitable electrically conductive material, and a pair of movable contact tips 85 supported at the ends of contact support 84, extends through the interior of plunger housing 79 and projects outwardly therefrom through slots 81 on either side of housing 79 so as to be substantially at right angles to the plane of the correspondingly adjacent opposing sidewalls 82 and 83, respectively. As viewed with reference to FIG. 8 of the drawings, the movable contact tips 85 both face outwardly, i.e., upwardly. Also, it is seen with reference to FIG. 9 of the drawings that the convertible contact assembly 68 is located at the upper end of slots 81 which represents the position which the convertible contact assembly 68 occupies when the components of the adder block 12 are arranged such as to provide the latter with a normally closed electrical circuit, i.e., as illustrated in FIG. 6 of the drawings. Spring 86 which is housed within a hollow cavity suitably provided for this purpose in the interior of the plunger housing 79 has one end in engagement with the bight portion of substantially U-shaped member 87 and the other end in engagement with contact support 84 of convertible contact assembly 68 whereby the spring 86 biases the convertible contact assembly 68 to the aforesaid upper end of slots 81 as viewed with reference to FIG. 9.

U-shaped member 87 which is slightly longer in length than the contact support 84 of convertible contact assembly 68 also extends through the interior of housing 79 of plunger 69 and projects outwardly therefrom through slots 81. Spring 86 biases the member 87 downwardly into engagement with the lower end wall surface of slots 81 as can best be seen with reference to FIG. 9 of the drawings. With the plunger 69 positioned in the interior of housing 63 of adder block l2-as illustrated in FIG. 6 of the drawings, the end portions of member 87 rest on a pair of ledges 88 suitably provided for this purpose within the interior 64 of housing 63 By virtue of this arrangement, when the plunger 69 is moved by an external force in a downwardly direction as viewed with reference to FIG. 6 of the drawing, spring 86 becomes compressed between member 87 and contact support 84 since the member 87 is retained against movement by its engagement with the ledges 88 while the contact support 84 is prevented from moving relative to the plunger housing 79 because of its engagement with the upper end wall surface of slots 81. Upon removal of the external force, spring 86 will return the convertible contact assembly 68 to the position illustrated in FIG. 6 of the drawings when the spring 44 returns plunger 69 and plunger 23 to their unactuated position. To facilitate the aforesaid movement'of the plunger 69 as well as for purposes of guiding the plunger 69 in its movement, the latter is preferably provided with a projection 89 located on sidewall 82 of the plunger 69. A suitable guiding slot (not shown) is provided in sidewall 63b of housing 63 of adder block 12 to receive the projection 89.

Insofar as assembling the various component parts of the adder block 12 is concerned, the normally closed and the normally open stationary contact assemblies 67 and 66, respectively, are first positioned within the interior 64 of housing 63 of adder block 12 as illustrated in FIG. 6 of the drawing.

Thereafter, if it is desired that the electrical circuit of the adder block 12 have a normally closed mode of operation, the convertible contact assembly 68 and the member 87 are arranged so as to bear the relationship to plunger housing 79 depicted in FIGS. 6, 8, and 9 of the drawings. If a normally open mode of operation is desired, then the convertible contact assembly 68 and the member 87 will be supported on the plunger 69 in the manner shown in FIG. 7 of the drawings. It is important to note however that in changing from a normally open to a normally closed mode of circuit operation or vice versa that the plunger housing 79 does not change position relative to the housing 65 of the adder block 12 but rather it is the convertible contact assembly 68 and the member 87 supported on the plunger housing 79 which are rearranged. This is in large part because the structural configuration of the slots 81, etc., of the plunger housing 79 are not symmetrical. More specifically, it is necessary in changing from a normally closed mode of circuit operation as depicted in FIG. 8 of the drawings to a normally open mode of circuit operation as depicted in FIG. 7 of the drawings, to remove both the convertible contact assembly 68 and the U-shaped member 87 from the slots 81 and thereafter reposition them in the slots 81 such that the member 87 now occupies the position occupied by the convertible contact assembly 68 in FIG. 8 and the convertible contact assembly 68 occupies the position occupied by the member 87 in the same figure. With the convertible contact assembly 68 and the member 87 positioned relative to the plunger 69 so as to provide the desired mode of circuit operation, the plunger 69 is then positioned within the interior 64 of housing 63 of adder block 12. Subsequently the previously described cover for open sidewall 65 of housing 63 is placed in juxtaposed relation to the open sidewall 65 and secured in place by suitable means such as a pair of screws (not shown) which pass through suitable openings provided for this purpose in the aforementioned cover and are threaded into the threaded openings 90 provided for this purpose in housing 63 of adder block 12.

For purposes of mounting the adder block 12 to the basic block 11, the basic block 11 is provided with a pair of essentially T-shaped slots 91 as shown in FIGS. 1 and 10, each slot being intended to receive a fastening means carried by the adder block 12. The latter fastening means preferably consists of a screw 92 and a nut 93 shown in FIG. 10. The screw 92 includes an externally threaded portion 92a and an internally threaded portion 92b. To assemble the screw 92 on the adder block 12, the screw 92 is passed through a suitable opening (not shown) provided for this purpose in adder block housing 63 and is then positioned in slot 94 in housing 63. Thereafter each of the nuts 93 is loosely threaded on to the end of each of the screws 92. Now to secure the adder block 12 to the basic block 11, the pair of nuts 93 are positioned in the head portion of T-shaped slots 91 of basic block 11. At the same time, one of the hooklike portions 80 of plunger 69 of adder block 12 is brought into engagement with the hooklike portion 42 of plunger 23 of basic block 11. Once the hooklike portions 80 and 42 are engaged, the screws 92 are tightened to securely fasten the adder block 12 and the basic block 11 together. The relationship between the sidewall dimensions of the head portion of the T-shaped slots 91 and the external dimensions of the nuts 93 are such that the nuts 93 are retained in slots 91 against rotation when the screws 92 are rotated for purposes of tightening the latter. In addition, in accordance with the preferred embodiment of the invention, housing 13 of basic block 11 is provided with a pair of projections 95 which cooperate with a pair of notches 96 provided in housing 63 of adder block 12 so as to form an interlocking means therebetween whereby to add to the rigidity between the adder block 12 and the basic block 11 when the latter blocks 11 and 12 are secured together.

With the adder block 12 and the basic block 11 secured together in the aforesaid manner. basic block 11 may be mounted to the sidewall casing of a magnetic motor starter in the manner earlier described. Inasmuch as the plunger 69 of adder block 12 and the plunger 23 of basic block 11 are interengaged through their hooklike portions or lugs and 42, respectively, so as to move as a unit, any movement of the plunger 23 will be transmitted to plunger 69 causing the latter to also move. Depending on whether the normal state of operation of the electric circuit of adder block 11 is normally open or normally closed, the plunger 69 of adder block 12 when caused to move by virtue of movement of the plunger 23 of basic block 11 will either close or open the contacts of the adder block electrical circuit. Further, it is seen that when the adder block 12 is secured to the basic block and the latter is mounted on a motor starter, the respective condition of the one electrical circuit of the adder block 12 and the two electrically separate circuits of basic block 11 is dependent on the operating condition of the motor starter. To add a second adder block 12 to the basic block 11, the above-described procedure is followed except that the screws 92 of the second adder block 11 are threaded into the internally threaded portions 92b of the screws 92 of the first adder block rather than into nuts 93.

Thus, in accordance with the present invention there has been provided a novel and improved switching device for electromagnetic control devices such as magnetic motor starters. The subject switching device is embodied in a housing which remains of the same size regardless of the size of the motor starter with which the switching device is employed. In addition, the switching device of the present invention has the capability of being mounted to a motor starter at the point of use rather than at the point of manufacture and also for purposes of mounting does not require the use of any special tools or equipment. Further, the switching device is constructed so as to provide either NO or NC contact operation at the option of the user, the user being permitted to exercise this option at the point of use rather than at the time of purchase. Also, the said switching device may be mechanically interconnected in series with other similarly constructed switching devices and then mounted to a motor starter whereby the number of additional control circuits with which the motor starter is provided may be augmented. While the switching device of the present invention possesses all of the aforesaid features, it is nevertheless relatively inexpensive to manufacture and is capable of providing reliability and ease of operation.

While only one embodiment has been shown, it will be appreciated that many modifications thereof may readily be made by those skilled in the art. For example, for those applications wherein only one circuit is to be utilized, the basic block 11 may be provided with only one set of stationary contacts, i.e., either contacts 25 or contacts 33 and only one set of cooperable movable contacts, i.e., either movable contacts 51 or movable contacts 54, respectively. I therefore intend by the appended claims to cover the above modifications as well as all other modifications which fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A switching device, mountable on a sidewall of an electromagnetic control device such as a magnetic motor starter having an externally accessible movable member, comprising:

a. an insulating housing having a substantially hollow interior, and at least one open sidewall;

b. said insulating housing further including a pair of opposed barriers extending into said hollow interior to provide said hollow interior with a first pair of compartmentlike hollow segments and a second pair of compartmentlike hollow segments, and an elongated opening interconnecting said first pair of compartmentlike hollo'yv segments with said second pair of compartmentlike hollow segments;

0. a cover of insulating material closing said open sidewall of said housing, said cover having a slot therein;

d. a first stationary contact means including a first stationary contact assembly;

contact tip supported at one end of said first electrically conductive contact support and a first terminal means supported at the other end of said first electrically conductive contact support;

. first retaining means retaining said first stationary contact assembly in abutting relation to one surface of one of said pair of opposed barriers with said first stationary contact tip positioned in one of said first pair of compartmentlike hollow segments in juxtaposed relation to said elongated opening and with said first terminal means positioned externally of said housing for easy accessibility thereto:

a second stationary contact means including a second stationary contact assembly;

said second stationary contact assembly comprising a second electrically conductive contact support, a second stationary contact tip supported at one end of said second electrically conductive contact support and a second terminal means supported at the other end of said second electrically conductive contact support;

. said second elcctricallyconductive contact support comprising a substantially Z-shaped member;

. second retaining means retaining said second stationary contact assembly in abutting relation to another surface of said one of said pair of opposed barriers with said second stationary contact tip positioned in one of said second pair of compartmentlike hollow segments in juxtaposed relation to said elongated opening and with said second terminal means positioned externally of said housing for easy accessibility thereto;

a plunger supported in said elongated opening of said housing for movement relative thereto, said plunger having a pair of end surfaces, and at least first, second, and third sidewalls, said third sidewall extending at right angles to said first and second sidewalls;

. said plunger further including a first pair of openings provided in said first and second sidewalls, a first hollow cavity communicating with said first pair of openings, a second pair of openings provided in said first and second sidewalls in spaced relation to said first pair of openings, a second hollow cavity communicating with said second pair of openings, a lug projecting outwardly from said third sidewall and through said slot in said cover for engagement with said externally accessible movable member of said magnetic motor starter, and a hooklike portion formed on one of said end surfaces of said plunger and accessible externally of said housing for engagement with a second switching device;

m. a first movable contact assembly including a first movable electrically conductive contact support and a first movable contact tip supported at one end of said first movable electrically conductive contact support;

said first movable electrically conductive contact support extending through said first hollow cavity and projecting outwardly through said first pair of openings with said first movable contact tip positioned externally of said plunger for movement in said one of said first pair of compartmentlike hollow segments into and out of contact with said first stationary contact tip;

first biasing means supported in said first hollow cavity of said plunger and biasing said first movable contact assembly for movement relative to said plunger;

a second movable contact assembly including a second movable electrically conductive contact support and a second movable contact tip supported at one end of said second movable electrically conductive contact support; said second movable electrically conductive contact support extending through said second hollow cavity and projecting outwardly through said second pair of openings with said second movable contact tip positioned externally of said plunger for movement in said one of said second pair of compartmentlike hollow segments into and out of engagement with said second stationary contact tip;

. second biasing means supported in said second hollow cavity of said plunger and biasing said second movable contact assembly for movement relative to said plunger;

. third biasing means supported at one end of said elongated housing for biasing said plunger and thereby said first and second movable contact assemblies to a first position wherein said first movable contact tip is out of contact with said first stationary contact tip thereby providing said switching device with a normally open electrical circuit and wherein said second movable contact tip is in contact with said second stationary contact tip thereby providing said switching device with a normally closed electrical circuit, said normally open electrical circuit and said normally closed electrical circuit being electrically separate; and

. motion of said externally accessible movable member of said magnetic motor starter being transmitted to said lug of said plunger to thereby move said plunger to a second position wherein as a result solely of said movement of said plunger to said second position said first movable contact tip is moved into contact with said first stationary contact tip and said second movable contact tip is moved out of contact with said second stationary contact tip.

A switching device, mountable on a sidewall of an electromagnetic control device such as a magnetic motor starter having an externally accessible movable member, as set forth in claim 1 wherein:

said first stationary contact means includes a third stationary contact assembly;

said third stationary contact assembly comprises a third electrically conductive contact support, a third stationary contact tip supported at one end of said third electrically conductive contact support and a third terminal means supported at the other end of said third electrically conductive contact support; and

. third retaining means retain said third stationary contact assembly in abutting relation to one surface of the other of said pair of opposed barriers with said third stationary contact tip positioned in the other of said first pair of compartmentlike hollow segments in juxtaposed relation to said elongated opening and with said third terminal means positioned externally of said housing for easy accessibility thereto.

A switching device, mountable on a sidewall of an electromagnetic control device such as a magnetic motor starter having an externally accessible movable member, as set forth in claim 2 wherein:

said first movable contact assembly includes a third movable contact tip supported at the other end of said first movable electrically conductive contact support; said third movable contact tip is positioned externally of said plunger for movement in said other of said first pair of compartmentlike hollow segments into and out of contact with said third stationary contact tip; and

said third movable contact tip is out of contact with said third stationary contact tip when said plunger is biased to said first position by said third biasing means.

A switching device, mountable on a sidewall of. an electromagnetic control device such as a magnetic motor starter having an externally accessible movable member, as set forth in claim 1 wherein:

the other of said pair of opposed barriers with said fourth stationary contact tip positioned in the other of said second pair of compartmentlike hollow segments in juxtaposed relation to said elongated opening and with said fourth terminal means positioned externally of said housing for easy accessibility thereto.

projecting outwardly from said third sidewall for engagement with said externally accessible movable member of said magnetic motor starter, and a hooklike portion formed on one of said end surfaces of said plunger of said first switch means; l

. said first switch means further including a first movable 5. A switching device, mountable on a sidewall of an electromagnetic control device such as a magnetic motor starter having an externally accessible movable member, as set forth in claim 4 wherein:

a. said second movable contact assembly includes a fourth movable contact tip supported at the other end of said second movable electrically conductive contact support;

b. said fourth movable contact tip is positioned externally of said plunger for movement in said other of said second pair of compartmentlike hollow segments into and out of contact with said fourth stationary contact tip; and

c. said fourth movable contact tip is in contact with said fourth stationary contact tip when said plunger is biased to said first position by said third biasing means.

6. A switching device, mountable on a sidewall of an electromagnetic control device such as a magnetic motor starter having an externally accessible movable member, comprising:

a. a first switch means including an insulating housing havcontact assembly means, a second movable contact assembly means, a first biasing means, a second biasing means, and a third biasing means;

h. said first movable contact assembly means of said first switch means including a first movable electrically conductive contact support and a first movable contact tip supported at one end of said first movable electrically conductive contact support;

i. said first movable electrically conductive contact support of said first movable contact assembly means of said first switch means extending through said first hollow cavity of said plunger of said first switch means and projecting outwardly through said first pair of openings thereof with said first movable contact tip of said first movable contact assembly means of said first switch means positioned externally of said plunger of said first switch means for movement in said one of said first pair of compartmentlike hollow segments of said first switch means into and ing a substantially hollow interior and a longitudinally extending slot, said insulating housing including a pair of opposed barriers extending into said hollow interior to provide said hollow interior with a first pair of compartout of contact with said first stationary contact tip of said first stationary contact assembly means of said first switch means;

j. said first biasing means of said first switch means being mentlike hollow segments and a Second pair of compartsupported in said first hollow cavity of said plunger of said mentlike hollow segments, and said longitudinally extendfirst switch means and biasing said first movable contact ing slot interconnecting said first pair of compartmentlike assembly means of said first switch means for movement hollow segments with said second pair of compartmentrelative to said plunger of said first switch means; like hollow segments; said second movable contact assembly means of said first said first switch means further including afirst stationary switch means including a second movable electrically contact assembly means supported in at least one of said conductive contact support and a second movable confirst pair of compartmentlike hollow segments, a second tact tip supported at one end of said second movable elecstationary contact assembly means supported in at least trically conductive contact support; one of said second pair of compartmentlike hollow seg- I. said second movable electrically conductive contact supments, and a plunger supported in said longitudinally export of said second movable contact assembly means of tending slot of said insulating housing for movement relasaid first switch means extending through said second holtive thereto; low cavity of said plunger of said first switch means and said first stationary contact assembly means of said first projecting outwardly through said second pair of switch means including afirst electrically conductive conopenings thereof with said second movable contact tip of tact support retained in abutting relation to one surface of said second movable contact assembly means of said first one of said pair of opposed barriers, a first stationary conswitch means positioned externally of said plunger of said tact tip supported at one end of said first electrically confirst switch means for movement in said one of said ductive contact support and positioned in said one of said second pair of compartmentlike hollow segments of said first pair of compartmentlike hollow segments, and a first first switch means into and out of contact with said terminal means supported at the other end of said first second stationary contact tip of said second stationary electrically conductive contact support and positioned contact assembly means of said first switch means; externally of said housing for easy accessibility thereto; in. said second biasing means of said first switch means d. said second stationary contact assembly means of said being supported in said second hollow cavity of said first switch means including a second electrically conducplunger of said first switch means and biasing-said-second tive contact support retained in abutting relation to movable contact assembly means of said first switch another surface of said one of said pair of opposed barmeans for movement relative to said plunger of said first riers, a second stationary contact tip supported at one end switch means; of said second electrically conductive contact support said third biasing means of said first switch means supand positioned in said one of said second pair of compartported in said hollow interior of said insulating housing of mentlike hollow segments, and a second terminal means said first switch means for biasing said plunger of said first supported at the other end of said second electrically conswitch means to a first position wherein said first movable ductive contact support and positioned externally of said contact tip of said first movable contact assembly means housing for easy accessibility thereto; of said first switch means is out of contact with said first said plunger of said first switch means having a pair of end stationary contact tip of said first stationary contact assurfaces, and at least first, second, and third sidewalls, sembly means of said first switch means thereby providing said third sidewall extending at right angles to said first said first switch means with a normally open electrical cirand second sidewalls; cuit and wherein said second movable contact tip of said f. said plunger of said first switch means further including a second movable contact assembly means of said first first pair of openings provided in said first and second switch means is in contact with said second stationary sidewalls thereof, a first hollow cavity communicating contact tip of said stationary contact assembly means of with said first pair of openings, a second pair of openings said first switch means thereby providing said first switch provided in said first and second sidewalls in spaced relameans with a normally closed electrical circuit, said nortion to said first pair of openings, a second hollow cavity mally open and said normally closed electrical circuits of communicating with said second pair of openings, a lug said first switch means being electrically separate;

0. motion of said externally accessible movable member of said magnetic motor starter being transmitted to said lug of said plunger of said first switch means to thereby move said plunger of said first switch means to a second position wherein as a result solely of said movement of said plunger of said first switch means to said second position said first movable contact tip of said first movable contact assembly means of said first switch means is moved into contact with said first stationary contact tip of said first stationary contact assembly means of said first switch means and said second movable contact tip of said second movable contact assembly of said first switch means is moved out of contact with said second stationary contact tip of said second stationary contact assembly means of said first switch means;

p. a second switch means including an insulating housing having a substantially hollow interior and a longitudinally extending slot, a first stationary contact assembly means supported in said hollow interior of said insulating housing, a second stationary contact assembly means supported in said hollow interior of said insulating housing, a plunger supported in said longitudinally extending slot of said insulating housing for movement relative thereto, a convertible movable contact assembly means, and a first biasing means;

. said plunger of said second switch means having at least first, second, and third sidewalls, and a pair of end surfaces;

. said plunger of said second switch means further including a pair of openings provided in said first and second sidewalls thereof, a hollow cavity communicating with said pair of openings, and a hooklike portion formed on each end surface of said plunger of said second switch means;

. one of said hooklike portions of said plunger of said second switch means being interconnected with said hooklike portion of said plunger of said first switch means to permit said plunger of said second switch means and said plunger of said first switch means to move in unison;

t. said convertible movable contact assembly means of said second switch means mountable in a first position so as to extend through said hollow cavity of said plunger of said second switch means and to project outwardly through said pair of openings thereof whereby said convertible movable contact assembly means of said second switch means in said first position is in electrical contact with said first stationary contact assembly means of said second switch means to provide said second switch means with a normally closed electrical circuit electrically separate from said normally open and normally closed electrical circuits of said first switch means;

said convertible movable contact assembly means of said second switch means being mountable in a second position axially spaced from said first position so as to extend through said hollow cavity of said plunger of said second switch means and to project outwardly through said pair of openings thereof whereby said convertible movable contact assembly means of said second switch means in said second position is out of electrical contact with said second stationary contact assembly means of said second switch means to provide said second switch means with a normally open electrical circuit electrically separate from said normally open and normally closed electrical circuits of said first means; and

. said first biasing means of said second switch means biasing said convertible movable contact assembly means of said second switch means into contact with said first stationary contact assembly means of said second switch means when said convertible movable contact assembly means of said second switch means is in said first position and biasing said convertible movable assembly means of said second switch means out of contact with said second stationary contact assembly means of said second switch means when said convertible movable contact assembly means of said second switch means is in said second position.

7. A switching device, mountable on a sidewall of an electromagnetic control device such as a magnetic motor starter having an externally accessible movable member, comprising:

a. a basic block including an insulating housing having a b. said basic block further including a plunger movably mounted in said longitudinally extending slot of said insulating housing for movement relative thereto, a first pair of stationary contacts supported in said first pair of compartmentlike hollow segments of said insulating housing in juxtaposed relation to the path of movement of said plunger, each of said first pair of stationary contacts retained in abutting relationship with a surface of one of said pair of opposed barriers a first pair of movable contacts movably mounted on said plunger for movement relative thereto cooperable with said first pair of stationary contacts to provide said basic block with a normally open mode of circuit operation, a second pair of stationary contacts supported in said second pair of compartmentlike hollow segments of said insulating housing in spaced relation to said first pair of stationary contacts and in juxtaposed relation to the path of movement of said plunger, and a second pair of movable contacts movably mounted on said plunger for movement relative thereto cooperable with said second pair of stationary contacts to provide said basic block with a normally closed mode of circuit operation;

. said plunger of said basic block including a housing comprising a plurality of sidewalls and a pair of end surfaces, a lug projecting outwardly from one of said plurality of sidewalls, and a hooklike portion formed on one of said end surfaces;

d. means mounting said basicblock on a sidewall of said magnetic motor starter with said lug of said plunger of said basic block positioned in the path of movement of said externally accessible movable member of said magnetic motor starter for engagement therewith and movement thereby;

. at least one adder block including an insulating housing having a substantially hollow interior, a plunger movably mounted in said hollow interior of said insulating housing for movement relative thereto, a first pair of stationary contacts supported in said hollow interior of said insulating housing in juxtaposed relation to the path of movement of said plunger, a second pair of stationary contacts supported in said hollow interior of said insulating housing in spaced relation to said pair of stationary contacts and in juxtaposed relation to the path of movement of said plunger, and a pair of convertible movable contacts movably mounted alternatively on said plunger in a first position wherein said pair of convertible movable contacts cooperates with said first pair of stationary contacts to provide said adder block with a normally open mode of circuit operation or in a second position wherein said pair of convertible movable contacts cooperates with said second pair of stationary contacts to provide said adder block with a normally closed mode of circuit operation;

f. said plunger of said adder block including a housing having a pair of end surfaces, and a hooklike portion formed on at least one of said end surfaces; and

. means mounting said adder block to said basic block in end-to-end relation with said adder block and said basic block both lying in a common plane spaced from the plane of said magnetic motor starter to which said basic block is mounted and with said hooklike portion of said plunger of said adder block interconnected with said hooklike portion of said plunger of said basic block to permit said plunger of said adder and said plunger of said basic block to move in unison.

8. A switching device, mountable on a sidewall of an electromagnetic control device such as a magnetic motor starter having an externally accessible movable member, as set forth in claim 7 wherein:

a. said means mounting said adder block to said basic block comprises at least one fastening means supported on said adder block and at least one opening provided in said insulating housing of said basic block to receive said fastening means of said adder block;

b. said fastening means of said adder block comprises a said opening of said insulating housing of said basic block is substantially T-shaped in configuration with at least said nut of said fastening means of said adder block being received therein. 

1. A switching device, mountable on a sidewall of an electromagnetic control device such as a magnetic motor starter having an externally accessible movable member, comprising: a. an insulating housing having a substantially hollow interior, and at least one open sidewall; b. said insulating housing further including a pair of opposed barriers extending into said hollow interior to provide said hollow interior with a first pair of compartmentlike hollow segments and a second pair of compartmentlike hollow segments, and an elongated opening interconnecting said first pair of compartmentlike hollow Segments with said second pair of compartmentlike hollow segments; c. a cover of insulating material closing said open sidewall of said housing, said cover having a slot therein; d. a first stationary contact means including a first stationary contact assembly; e. said first stationary contact assembly comprising a first electrically conductive contact support, a first stationary contact tip supported at one end of said first electrically conductive contact support and a first terminal means supported at the other end of said first electrically conductive contact support; f. first retaining means retaining said first stationary contact assembly in abutting relation to one surface of one of said pair of opposed barriers with said first stationary contact tip positioned in one of said first pair of compartmentlike hollow segments in juxtaposed relation to said elongated opening and with said first terminal means positioned externally of said housing for easy accessibility thereto: g. a second stationary contact means including a second stationary contact assembly; h. said second stationary contact assembly comprising a second electrically conductive contact support, a second stationary contact tip supported at one end of said second electrically conductive contact support and a second terminal means supported at the other end of said second electrically conductive contact support; i. said second electrically conductive contact support comprising a substantially Z-shaped member; j. second retaining means retaining said second stationary contact assembly in abutting relation to another surface of said one of said pair of opposed barriers with said second stationary contact tip positioned in one of said second pair of compartmentlike hollow segments in juxtaposed relation to said elongated opening and with said second terminal means positioned externally of said housing for easy accessibility thereto; k. a plunger supported in said elongated opening of said housing for movement relative thereto, said plunger having a pair of end surfaces, and at least first, second, and third sidewalls, said third sidewall extending at right angles to said first and second sidewalls; l. said plunger further including a first pair of openings provided in said first and second sidewalls, a first hollow cavity communicating with said first pair of openings, a second pair of openings provided in said first and second sidewalls in spaced relation to said first pair of openings, a second hollow cavity communicating with said second pair of openings, a lug projecting outwardly from said third sidewall and through said slot in said cover for engagement with said externally accessible movable member of said magnetic motor starter, and a hooklike portion formed on one of said end surfaces of said plunger and accessible externally of said housing for engagement with a second switching device; m. a first movable contact assembly including a first movable electrically conductive contact support and a first movable contact tip supported at one end of said first movable electrically conductive contact support; n. said first movable electrically conductive contact support extending through said first hollow cavity and projecting outwardly through said first pair of openings with said first movable contact tip positioned externally of said plunger for movement in said one of said first pair of compartmentlike hollow segments into and out of contact with said first stationary contact tip; o. first biasing means supported in said first hollow cavity of said plunger and biasing said first movable contact assembly for movement relative to said plunger; p. a second movable contact assembly including a second movable electrically conductive contact support and a second movable contact tip supported at one end of said second movable electrically conductive contact support; q. said second movable electrically conductive contact support extending througH said second hollow cavity and projecting outwardly through said second pair of openings with said second movable contact tip positioned externally of said plunger for movement in said one of said second pair of compartmentlike hollow segments into and out of engagement with said second stationary contact tip; r. second biasing means supported in said second hollow cavity of said plunger and biasing said second movable contact assembly for movement relative to said plunger; s. third biasing means supported at one end of said elongated housing for biasing said plunger and thereby said first and second movable contact assemblies to a first position wherein said first movable contact tip is out of contact with said first stationary contact tip thereby providing said switching device with a normally open electrical circuit and wherein said second movable contact tip is in contact with said second stationary contact tip thereby providing said switching device with a normally closed electrical circuit, said normally open electrical circuit and said normally closed electrical circuit being electrically separate; and t. motion of said externally accessible movable member of said magnetic motor starter being transmitted to said lug of said plunger to thereby move said plunger to a second position wherein as a result solely of said movement of said plunger to said second position said first movable contact tip is moved into contact with said first stationary contact tip and said second movable contact tip is moved out of contact with said second stationary contact tip.
 2. A switching device, mountable on a sidewall of an electromagnetic control device such as a magnetic motor starter having an externally accessible movable member, as set forth in claim 1 wherein: a. said first stationary contact means includes a third stationary contact assembly; b. said third stationary contact assembly comprises a third electrically conductive contact support, a third stationary contact tip supported at one end of said third electrically conductive contact support and a third terminal means supported at the other end of said third electrically conductive contact support; and c. third retaining means retain said third stationary contact assembly in abutting relation to one surface of the other of said pair of opposed barriers with said third stationary contact tip positioned in the other of said first pair of compartmentlike hollow segments in juxtaposed relation to said elongated opening and with said third terminal means positioned externally of said housing for easy accessibility thereto.
 3. A switching device, mountable on a sidewall of an electromagnetic control device such as a magnetic motor starter having an externally accessible movable member, as set forth in claim 2 wherein: a. said first movable contact assembly includes a third movable contact tip supported at the other end of said first movable electrically conductive contact support; b. said third movable contact tip is positioned externally of said plunger for movement in said other of said first pair of compartmentlike hollow segments into and out of contact with said third stationary contact tip; and c. said third movable contact tip is out of contact with said third stationary contact tip when said plunger is biased to said first position by said third biasing means.
 4. A switching device, mountable on a sidewall of an electromagnetic control device such as a magnetic motor starter having an externally accessible movable member, as set forth in claim 1 wherein: a. said second stationary contact means includes a fourth stationary contact assembly; b. said fourth stationary contact assembly comprises a fourth electrically conductive contact support, a fourth stationary contact tip supported at one end of said fourth electrically conductive contact support and a fourth terminal means supported at the other end of said fourth electrically conductive contact support; and c. fourth retaining means retain said fourth stationary contact assembly in abutting relation to another surface of the other of said pair of opposed barriers with said fourth stationary contact tip positioned in the other of said second pair of compartmentlike hollow segments in juxtaposed relation to said elongated opening and with said fourth terminal means positioned externally of said housing for easy accessibility thereto.
 5. A switching device, mountable on a sidewall of an electromagnetic control device such as a magnetic motor starter having an externally accessible movable member, as set forth in claim 4 wherein: a. said second movable contact assembly includes a fourth movable contact tip supported at the other end of said second movable electrically conductive contact support; b. said fourth movable contact tip is positioned externally of said plunger for movement in said other of said second pair of compartmentlike hollow segments into and out of contact with said fourth stationary contact tip; and c. said fourth movable contact tip is in contact with said fourth stationary contact tip when said plunger is biased to said first position by said third biasing means.
 6. A switching device, mountable on a sidewall of an electromagnetic control device such as a magnetic motor starter having an externally accessible movable member, comprising: a. a first switch means including an insulating housing having a substantially hollow interior and a longitudinally extending slot, said insulating housing including a pair of opposed barriers extending into said hollow interior to provide said hollow interior with a first pair of compartmentlike hollow segments and a second pair of compartmentlike hollow segments, and said longitudinally extending slot interconnecting said first pair of compartmentlike hollow segments with said second pair of compartmentlike hollow segments; b. said first switch means further including a first stationary contact assembly means supported in at least one of said first pair of compartmentlike hollow segments, a second stationary contact assembly means supported in at least one of said second pair of compartmentlike hollow segments, and a plunger supported in said longitudinally extending slot of said insulating housing for movement relative thereto; c. said first stationary contact assembly means of said first switch means including a first electrically conductive contact support retained in abutting relation to one surface of one of said pair of opposed barriers, a first stationary contact tip supported at one end of said first electrically conductive contact support and positioned in said one of said first pair of compartmentlike hollow segments, and a first terminal means supported at the other end of said first electrically conductive contact support and positioned externally of said housing for easy accessibility thereto; d. said second stationary contact assembly means of said first switch means including a second electrically conductive contact support retained in abutting relation to another surface of said one of said pair of opposed barriers, a second stationary contact tip supported at one end of said second electrically conductive contact support and positioned in said one of said second pair of compartmentlike hollow segments, and a second terminal means supported at the other end of said second electrically conductive contact support and positioned externally of said housing for easy accessibility thereto; e. said plunger of said first switch means having a pair of end surfaces, and at least first, second, and third sidewalls, said third sidewall extending at right angles to said first and second sidewalls; f. said plunger of said first switch means further including a first pair of openings provided in said first and second sidewalls thereof, a first hollow cavity communicating with said first pair of openings, a second pair of openings provided in said first and second sidewalls in spAced relation to said first pair of openings, a second hollow cavity communicating with said second pair of openings, a lug projecting outwardly from said third sidewall for engagement with said externally accessible movable member of said magnetic motor starter, and a hooklike portion formed on one of said end surfaces of said plunger of said first switch means; g. said first switch means further including a first movable contact assembly means, a second movable contact assembly means, a first biasing means, a second biasing means, and a third biasing means; h. said first movable contact assembly means of said first switch means including a first movable electrically conductive contact support and a first movable contact tip supported at one end of said first movable electrically conductive contact support; i. said first movable electrically conductive contact support of said first movable contact assembly means of said first switch means extending through said first hollow cavity of said plunger of said first switch means and projecting outwardly through said first pair of openings thereof with said first movable contact tip of said first movable contact assembly means of said first switch means positioned externally of said plunger of said first switch means for movement in said one of said first pair of compartmentlike hollow segments of said first switch means into and out of contact with said first stationary contact tip of said first stationary contact assembly means of said first switch means; j. said first biasing means of said first switch means being supported in said first hollow cavity of said plunger of said first switch means and biasing said first movable contact assembly means of said first switch means for movement relative to said plunger of said first switch means; k. said second movable contact assembly means of said first switch means including a second movable electrically conductive contact support and a second movable contact tip supported at one end of said second movable electrically conductive contact support; l. said second movable electrically conductive contact support of said second movable contact assembly means of said first switch means extending through said second hollow cavity of said plunger of said first switch means and projecting outwardly through said second pair of openings thereof with said second movable contact tip of said second movable contact assembly means of said first switch means positioned externally of said plunger of said first switch means for movement in said one of said second pair of compartmentlike hollow segments of said first switch means into and out of contact with said second stationary contact tip of said second stationary contact assembly means of said first switch means; m. said second biasing means of said first switch means being supported in said second hollow cavity of said plunger of said first switch means and biasing said second movable contact assembly means of said first switch means for movement relative to said plunger of said first switch means; n. said third biasing means of said first switch means supported in said hollow interior of said insulating housing of said first switch means for biasing said plunger of said first switch means to a first position wherein said first movable contact tip of said first movable contact assembly means of said first switch means is out of contact with said first stationary contact tip of said first stationary contact assembly means of said first switch means thereby providing said first switch means with a normally open electrical circuit and wherein said second movable contact tip of said second movable contact assembly means of said first switch means is in contact with said second stationary contact tip of said stationary contact assembly means of said first switch means thereby providing said first switch means with a normally closed electrical circuit, said normally open and said normally closed electrical circuits of saId first switch means being electrically separate; o. motion of said externally accessible movable member of said magnetic motor starter being transmitted to said lug of said plunger of said first switch means to thereby move said plunger of said first switch means to a second position wherein as a result solely of said movement of said plunger of said first switch means to said second position said first movable contact tip of said first movable contact assembly means of said first switch means is moved into contact with said first stationary contact tip of said first stationary contact assembly means of said first switch means and said second movable contact tip of said second movable contact assembly of said first switch means is moved out of contact with said second stationary contact tip of said second stationary contact assembly means of said first switch means; p. a second switch means including an insulating housing having a substantially hollow interior and a longitudinally extending slot, a first stationary contact assembly means supported in said hollow interior of said insulating housing, a second stationary contact
 7. A switching device, mountable on a sidewall of an electromagnetic control device such as a magnetic motor starter having an externally accessible movable member, comprising: a. a basic block including an insulating housing having a substantially hollow interior, a longitudinally extending slot, and a pair of opposed barriers extending into said hollow interior to provide said hollow interior with a first pair of compartmentlike hollow segments and a second pair of compartmentlike hollow segments; b. said basic block further including a plunger movably mounted in said longitudinally extending slot of said insulating housing for movement relative thereto, a first pair of stationary contacts supported in said first pair of compartmentlike hollow segments of said insulating housing in juxtaposed relation to the path of movement of said plunger, each of said first pair of stationary contacts retained in abutting relationship with a surface of one of said pair of opposed barriers a first pair of movable contacts movably mounted on said plunger for movement relative thereto cooperable with said first pair of stationary contacts to provide said basic block with a normally open mode of circuit operation, a second pair of stationary contacts supported in said second pair of compartmentlike hollow segments of said insulating housing in spaced relation to said first pair of stationary contacts and in juxtaposed relation to the path of movement of said plunger, and a second pair of movable contacts movably mounted on said plunger for movement relative thereto cooperable with said second pair of stationary contacts to provide said basic block with a normally closed mode of circuit operation; c. said plunger of said basic block including a housing comprising a plurality of sidewalls and a pair of end surfaces, a lug projecting outwardly from one of said plurality of sidewalls, and a hooklike portion formed on one of said end surfaces; d. means mounting said basic block on a sidewall of said magnetic motor starter with said lug of said plunger of said basic block positioned in the path of movement of said externally accessible movable member of said magnetic motor starter for engagement therewith and movement thereby; e. at least one adder block including an insulating housing having a substantially hollow interior, a plunger movably mounted in said hollow interior of said insulating housing for movement relative thereto, a first pair of stationary contacts supported in said hollow interior of said insulating housing in juxtaposed relation to the path of movement of said plunger, a second pair of stationary contacts supported in said hollow interior of said insulating housing in spaced relation to said pair of stationary contacts and in juxtaposed relation to the path of movement of said plunger, and a pair of convertible movable contacts movably mounted alternatively on said plunger in a first position wherein said pair of convertible movable contacts cooperates with said first pair of stationary contacts to provide said adder block with a normally open mode of circuit operation or in a second position wherein said pair of convertible movable contacts cooperates with said second pair of stationary contacts to provide said adder block with a normally closed mode of circuit operation; f. said plunger of said adder block including a housing having a pair of end surfaces, and a hooklike portion formed on at least one of said end surfaces; and g. means mounting said adder block to said basic block in end-to-end relation with said adder block and said basic block both lying in a common plane spaced from the plane of said magnetic motor starter to which said basic block is mounted and with said hooklike portion of said plunger of said adder block interconnected with said hooklike portion of said plunger of said basic block to permit said plunger of said adder and said plunger of said Basic block to move in unison.
 8. A switching device, mountable on a sidewall of an electromagnetic control device such as a magnetic motor starter having an externally accessible movable member, as set forth in claim 7 wherein: a. said means mounting said adder block to said basic block comprises at least one fastening means supported on said adder block and at least one opening provided in said insulating housing of said basic block to receive said fastening means of said adder block; b. said fastening means of said adder block comprises a fastener and a nut, said fastener including at one end an externally threaded portion for threading said nut thereon and at the other end an internally threaded portion capable of receiving the externally threaded portion of a second fastener; and c. said opening of said insulating housing of said basic block is substantially T-shaped in configuration with at least said nut of said fastening means of said adder block being received therein. 